Automatic pressure control for low-temperature, low-pressure fractionating columns



Nov. 6, 1945. R. nousLl-N 2,388,312

AUTOMATIC PRESSURE CONTROL FOR LOW-TEMPERATURE, LOW-PRESSURE FRACTIONATING COLUMNS Filed Dec. 7, 1942 TO COMPRESSED AIR L|NE M OVERHEAD I TAKEOFF a 4 COOLING \l ZONE FRACTIONATING COLUMN COMPRESSED AIR LINE |2\ METER/ STICK VENT Y L /FLoAT|NG NEEDLE w VALVE l8 |2\ IOA- /MERCURY 19 2 [6 coNsTRlcTloN I IOA zzzz \PINCH FIG; 2

CLAMP INVENTOR v D. R. DOUSLIN Patented Nov. 6, 1945 AUTOMATIC PRESSURE CONTROL FOR LOW-TEMPERATURE, LOW-PRESSURE FRACTIONATING COLUMNS Donald R. Douslin, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application December 7, 1942, Serial No. 468,148

2 Claims. (Cl. 202-160) This invention relates to an automatic pressure controlled analytical fractionating apparatus and is particularlyapplicable, although not necessarily restricted, to the analysis of hydrocarbon gases and liquids or mixtures of hydrocarbon gases and liquids such as natural gas, natural gasoline, gasoline and other petroleum distillates or in fact any mixture of materials which is capable of analysis by distillation under conditions of low temperatures and pressures and especially where the pressure within the fractionating column must be very carefully controlled.

It is the purpose of this invention to provide a valve or similar device which is automatically operable directly in response to pressure fluctuation within the column to influence the air flow from a constant pressure source in such a manner as to force quantities of cooling agent to the condensing section and thereby regulate accurately the fractionation pressure. In some respects, the present invention is an improvement on the patent to W. J. Podbielniak No. 1,967,258, issued July 24, 1934. The arrangement described by Podbielniak includes a control device which is adapted to maintain a constant pressure in the column. A manometer which is connected with the vapor outlet tube by a sidearm .is provided with electrodes leading to an electrical circuit which includes a solenoid valve. The valve controls the eflective pressure applied from a source of constant air pressure to a body of liquid air in a flask. .In the operation of the Podbielniak arrangement, pressure increase in the fractionating column is registered on the mercury column of the manometer, closing the circuit through t e solenoid valve and applying pressure to the liquid air which is forced intothe cooling section of the column, thereby reducing the fractionation pressure. My invention, is a manifest improvement over the arrangement of the patent in providing fully automatic control of the fractionating pressure in an advantageous andexpedient manner and with the elimination of electrical circuits,

. solenoid valves and other relatively expensive equipment which have heretofore been considered essential to the operation of such devices.

Referring to the drawing:

Figure 1 is a general view of an analytical fractionating column and manometer incorporating my improvement.

Figure 2 is a sectional detail of the valve control shown in Figure 1.

With specific reference to Figure 1, I is an analytical fractionating column of the general type described in Podbielniak Patent 1,967,258,

having heating element 2 and a cooling zone 3 forming a receptacl at the top of the column provided with an outlet 4 and inlet conduit 5 connected with a supply. 6 of liquid air or nitrogen, which is adapted to be forced by compressed air pressure through conduit 1 into the cooling section in an amount proportionate to pressure variation in the fractionating column in a manner hereinafter described. The overhead vapors from the fractionating process pass through conduit 8 to an accumulator not shown. Conduit 8 is provided'with a side arm 9 which connects with a mercury manometer l0 fixed to the meter stick I l. The arm IOA of the manometer connects with conduit I and is provided with a floating needle valve designated generally at l2 in Figure 1 and shown in detail in Figure 2. As clearly shown in Figure 2, arm "1A is vented to the atmosphere through air vent l3 and has an elongated relatively restricted section l4 through which the head l5 of the needle valve will barely pass. The needle valve may be formed of any suitable material either solid or hollow according to the spe-' sure. It will be understood that the inside diameter of the restricted portion ll of the arm IDA is slightly greater than the outside diameter of the needle valve head l5, so as to allow a continuous small flow of air through the vent, the

magnitude of which is dependent on the position of the needle valve l2. A leveling bottle l8 having a pinch clamp I9 is connected with the manometer tube III at the bend thereof.

In operation, heat is applied to the bottom of the fractionating column and overhead vapors pass through the line 8 to the accumulator, not shown. The pressure variation in the fractionating column is registered on the manometer column fluid which cause the needle valve to rise and fall relative to the restricted portion ll. The quantity of air under constant pressure from air line I! passing head l5 to the bent l3. and likewise the pressure imposed on the liquid air supply 6, is therefore, a function'of the pressure in the fractionating column. It is therefore ob vious that increase of pressure in the fractionating column will force an increased quantity of liquid air into the cooling zone 3 reducing the pressure in the column. During normal operation and while the pressure in the column is constant a small quantity ,of liquid air is continuously forced into the cooling zone. By regulation of the compressed air pressure admitted at l1 and by adjusting the mercury level with the leveling bottle l8 it is possible to fractionate under any desired constant pressure automatically and without attention of the operator.

portion of the column, a second conduit conducting cooling liquid from the supply to the heat exchanger in response to said pressure, a bleed valve in said first conduit for varying the pressure therein, and means responsive to the pressure in said distilling column for varying the opening of said bleed valve whereby the amount of cooling liquid entering said heat exchanger is varied so as to keep said pressure in said distilling column substantially constant.

2. In a fractional distilling apparatus the combination comprising a source of fluid under constant pressure, a first conduit connecting said source and a supp y of cooling liquid, a distillin column, a heat exchanger for cooling the upper portion of the column, a second conduit conducting cooling liquid from the supply to theheat exchanger in response to said pressure, a bleed valve in said first conduit for varying the pressure therein, a U tube communicating at one end with the distilling column and at the other end with said first conduit, a heavy liquid in the lower part of the U tube responsive to the pressures in the first conduit and the distilling column through the respective ends of the U tube, said bleed valve including a valve head floating in said heavy liquid, whereby the amount of cooling liquid entering said heat exchanger is varied so as to keep said pressure in said distilling column substantiallyconstant.

DONALD R. DOUSLIN. 

